1. Field of the Invention
The present invention relates to a manual valve for controlling fluid by rotating a knob manually and particularly to a manual valve for controlling chemical liquid or the like to be used in a semiconductor manufacturing device.
2. Description of Related Art
Heretofore, a manual valve has been employed in a semiconductor manufacturing device, for example, as a chemical liquid valve for controlling flow of a chemical liquid to be supplied to a chemical liquid supply unit or as a chemical liquid collecting valve or the like for sampling a chemical liquid. Among such manual valves, some manual valves are designed such that a valve element is moved by rotation of a knob through a rod (see Japanese Unexamined Patent Application Publication No. 2004-324661 and Japanese Unexamined Patent Application Publication No. 2005-344918).
An explanation for a manual valve disclosed in JP2004-324661A is now given referring to FIG. 16.
A manual valve 301A is constituted of a valve main body 303, a diaphragm retainer 304, a cylinder 305, a diaphragm valve element 309, a valve rod 310, a knob 312A, and others. The diaphragm valve element 309 (valve element) includes a peripheral portion firmly held between the valve main body 303 and the diaphragm retainer 304 and is threaded with the valve rod 310 in a center portion thereof. The valve rod 310 is continuously urged upward by a spring 311. The knob 312A having a surface contact with an upper end portion of the valve rod 310, is threadedly engaged with the cylinder 305.
In the manual valve 301A of JP2004-324661A, when the knob 312A is turned to move upward/downward as being held in contact with the valve rod 310, the valve rod 310 is moved in an opening/closing direction against the urging force of the spring 311, so that a valve opening degree can be adjusted.
Then, a manual valve disclosed in JP2005-344918A is explained referring to FIG. 17.
A manual valve 401 is constituted of a handle (knob) 411, a sliding nut 413, a piston 423, a spring 426, a valve element 433, a valve seat 434, and others.
A thread portion 413a of the sliding nut 413 is threadedly engaged with a thread portion 423a of the piston 423 to connect the sliding nut 413 with the piston 423, so that the sliding nut 413 is rotated integrally with the handle 411. The valve element 433 includes a peripheral end portion 433a which is firmly held between the valve main body 431 and a lower piston cylinder 423 and is integrally connected with the piston 423 in its center portion. The piston 423 is continuously urged downward by a metal-made spring 426.
In the manual valve 401 of JP2005-344918A, when the handle 411 is rotated in a valve closing direction, the piston 423 is moved downward by screw feeding with respect to the sliding nut 413 to bring the valve element 433 downward into contact with the valve seat 434 by the urging force of the spring 426. When the valve element 433 is placed in contact with the valve seat 434 into a valve closing position, the thread portion 413a of the sliding nut 413 and the thread portion 423a of the piston 423 are disengaged, so that the handle 411 turns free.
In the manual valve as disclosed in JP2004-324661A, the rod is threadedly moved by rotation of the knob while the rod is in contact with the knob, thereby moving the valve element. However, in a valve closing operation by turning the knob, the knob could be rotated more than necessary by excessive torque even after the valve element came to contact with the valve seat. Then, the valve element connected integrally with the piston could excessively press the valve seat, resulting in damages such as deformation or breakage of the valve seat.
Moreover, since the manual valve of JP2005-344918A is designed so that the valve element is brought into contact with the valve seat by the urging force of the spring to close the valve, the manual valve tends to be complicated in structure and increase in the number of components, leading to cost increase.
Further, installation of the spring causes upsizing of the manual valve, making it difficult to minimize a size of the manual valve. Furthermore, since the metal-made spring is provided to make the valve element into contact with the valve seat for the valve closing, there is a possibility that leaking chemical liquid intrudes into the manual valve from a peripheral portion of the knob, and such chemical liquid could contact with or attach to the spring. Accordingly, the spring suffers from deterioration, erosion, rust or the like caused by the leaking chemical liquid, and thus the manual valve could fail to close appropriately.